The present invention relates to a pump for pumping fluid, to a fluid separation apparatus, and to a method of operating a pump.
In a sample separation device based on the principle of liquid chromatography, a fluidic sample to be separated is injected in a mobile phase (such as a solvent composition), wherein the mixture may be pumped through conduits and a column comprising a material (stationary phase) which is capable of separating different components of the fluidic sample. Such a material, so-called beads which may comprise silica gel, may be filled into a column tube which may be connected to other elements (like a sampling unit, a flow cell, containers including sample and/or buffers) by conduits.
For pumping a fluid constituted by the mobile phase and the fluidic sample to be separated to the sample separation device, a pump may be implemented in which a piston reciprocates within a pumping chamber to thereby displace the fluid.
U.S. Pat. No. 5,788,465 discloses a pump configured so that tools are not required to remove the pump head and disassemble the plunger. A single large hand operated knob or head nut facilitates tool-less pump head removal. The pump head is guided into position in a manifold and held in place by the hand knob. The manifold is designed to receive all the external fluidic connections made to the pump head. Fluid paths to the pump head have been replaced with miniature face seals which facilitate high pressure sealing between the pump head and manifold. Low pressure tubing seals reside in a seal wash chamber or housing and are not attached to the head, eliminating the need for tooling to disconnect them during pump head removal. A tool-less plunger mechanism includes a nutcap assembly having a plunger socket receiving a plunger assembly including a sapphire plunger fixed to a plunger holder ball accommodated by the socket. The plunger assembly is captured within the socket by a plurality of cams. The cams are spring loaded to rotate and collapse onto the plunger holder ball, pulling the plunger assembly tightly into the socket. A restricting cone is actuated to rotate the cams away from the plunger holder ball for release and removal of the plunger assembly.
However, when the pressure values according to which fluid is pumped by the pump become larger and larger, a mechanically stable pump is required which is at the same time able to deal with part and interface tolerances, in particular while mounting or maintaining the pump.